Lubricating compositions

ABSTRACT

THE COMPOSITION OF THE INVENTION ARE LUBRICATING OILS COMPRISING A MAJOR PROPORTION OF A MINERAL OIL OF LUBRICATING VISCOSITY AND A MINOR PROPORTION OF A COMBINATION OF ADDITIVES (A) AND (B), ADDITIVE (A) BEING A NITROGEN-FREE RANDOM COPOLYMER OF ONE OR MORE ALKYL METHACRYLATES AND ONE OR MORE ALKYL ACRYLATES, THE COPOLYMER BEING COMPOSED OF UP TO 65% ALKYL ACRYLATE UNITS BASED ON THE TOTAL NUMBER OF ALKYL METHACRYLATE AND ALKYL ACRYLATE UNITS PRESENT IN THE COPOLYMER AND ADDITIVE (B) BEING AN ALKALINE EARTH METAL CONTAINING DETERGENT HAVING A TOTAL BASE NUMBER GREATER THAN 40.

United States Patent O US. Cl. 252-33.4 8 Claims ABSTRACT OF THE DISCLOSURE The compositions of the invention are lubricating oils comprising a major proportion of a mineral oil of lubricating viscosity and a minor proportion of a combination of additives (a) and (b), additive (a) being a nitrogen-free random copolymer of one or more alkyl methacrylates and one or more alkyl acrylates, the copolymer being composed of up to 65% alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units present in the copolymer and additive (b) being an alkaline earth metal containing detergent having a total base number greater than 40.

This invention relates to lubricating compositions, more particularly to lubricating compositions containing viscosity index improvers based on polymers of alkyl esters of unsaturated acids.

One of the most widely used groups of viscosity index improvers is based on copolymers of alkyl methacrylates, particularly copolymers of one or more relatively short chain alkyl methacrylates, such as butyl methacrylate, with one or more relatively long chain alkyl methacrylates, such as stearyl methacrylate.

However, the commonly used polymethacrylate viscosity index improvers display certain undersirable properties. In particular such polymethacrylates tend to derate the performance characteristics of simple mineral oil blends with regard to engine cleanliness, i.e. the polymethacrylates are a source of soot and dirt. This can be counteracted, at least to some extent, by adding a detergent to the mineral oil blends or by increasing the concentration of detergent if already present. However, it will be apparent that an alternative additive having comparable potency with regrad to viscosity index properties to the polymethacrylates but having greater thermal stability, i.e. less tendency to form thermal degradation products such as soot, will enable the amount of detergent employed to be reduced or engine cleanliness at the same additive dosage to be improved.

Various alternatives to polymethacrylate viscosity index improvers have been suggested but these also suffer from attendant drawbacks. For example, styrene/methacrylate copolymers have greater thermal stability than polymethacrylates on the basis of laboratory evaluation techniques such as thermogravimetric analysis. Nevertheless, in practice, these copolymers tend to derate performance characteristics of lubricant compositions with regard to engine cleanliness because the pendant aromatic groups on the copolymer chains are a source of carbon deposition. Similarly, polyacrylates have been proposed, as alternatives to polymethacrylates, but have been found to be unstable in the presence of basic additives, particularly overbased detergents, commonly present in fully formulated mineral oil blends. Hydrolysis of the polyacrylate can occur accompanied by gel formation. This problem can be especially troublesome in the preparation of additive packages having a high content of additives and which are intended to be diluted with mineral oil before use.

Accordingly, the provision of an improved lubricating Patented Jan. 29, 1974 ice composition is a complex task requiring careful consideration of several mutually interacting factors. The lubricating compositions of the present invention, or at least the preferred embodiments thereof, have viscosity indices comparable to those of similar compositions containing polymethacrylate viscosity index improvers, improved characteristics with respect to engine cleanliness and superior stability at high temperatures. Furthermore, the additive packages of the present invention have a reduced tendency to form gels.

According to the present invention there is provided a lubricating composition comprising a major proportion of a mineral oil of lubricating viscosity and a minor proportion of a combination of additives (a) and (b), additive (a) being a nitrogen-free random copolymer of one or more alkyl methacrylates and one or more alkyl acrylates, preferably prepared by copolymerizing one or more alkyl methacrylate comonomers with one or more alkyl acrylate comonomers, the copolymer being composed of up to 65% alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units present in the copolymer and additive (b) being an alkaline earth metal containing detergent having a total base number greater than 40.

It is to be understood that the percentages of monomer units set out above, and the percentages of monomer units referred to hereinafter, are equal to the mole percentages of polymerized monomer in additive (a).

The copolymer which constitutes additive (a) may be composed of from 5 to 40% alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units. In a particularly preferred embodiment the copolymer is composed of from 10 to 30%, more preferably 15 to 25%, alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units.

The alkyl acrylate units may contain from 4 to 21 carbon atoms. In one aspect of the invention the alkyl acrylate units contain from 4 to 15, preferably 6 to 12 carbon atoms. Butyl acrylate and 2-ethylhexyl acrylate are particularly preferred examples of such acrylate units. In another aspect of the invention it is especially preferred to use acrylate units containing 4 or 5 carbon atoms, that is methyl and/or ethyl acrylate in conjunction with certain methacrylate units hereinafter described.

The alkyl methacrylate monomer or monomers used in the preparation of the copolymer, may be any of the alkyl methacrylates, or mixtures of alkyl methacrylates, commonly used in the preparation of polymethacrylate viscosity index improvers, for example alkyl methacrylates containing from 5 to 22 carbon atoms. Examples of methacrylate monomer mixtures commonly employed are mixtures of 5 to 20% by weight C alkyl methacrylates and to by weight 0 alkyl methacrylates; mixtures of 10 to 20% by weight C alkyl methacrylates, 40 to 55% by weight 0 alkyl methacrylates and 35 to 45% by weight C alkyl methacrylates; and mixtures of 5 to 10% by weight methyl methacrylate, 5 to 10% by Weight branched chain (35-10 alkyl methacrylates and 80 to 90% by weight 0 alkyl methacrylates. A particularly preferred alkyl methacrylate monomer mixture is a mixture of about 60 mole percent butyl methacrylate and about 40 mole percent mixed cetyl and stearyl methacrylate. When copolymerized with methyl and/or ethyl acrylate units it is particularly preferred that the methacrylate units comprise at least 50% C alkyl methacrylate units. It is preferred that the C alkyl methacrylate units at least 50% are C31g alkyl methacrylate units. The remainder of the methacrylate units, if any, may be higher alkyl methacrylate units such as C units e.g. C or C methacrylate units.

The copolymer may be present in the lubricating composition of the present invention in the proportions in 3 which viscosity index improvers are commonly employed, for example 0.5 to 7.5%, preferably 1 to 5% by weight based on the total weight of the composition.

Additive (b) must have a basicity, expressed as total base number (TBN), greater than 40. Examples of additive (b) are overbased alkaline earth metal salts, particularly calcium, barium and magnesium salts, of alkyl benzene and petroleum sulphonic acids. Such overbased salts may have a TBN of up to 500 to 600, for example 250 to 400. Other basic additives are overbased alkaline earth metal salts, particularly barium salts, of phosphosulphurized hydrocarbons, for example polyisobutylenes. These salts may be overbased by carbonation of an alkaline earth metal oxide or hydroxide suspended in a mineral oil blend containing the phosphosulphurized hydrocarbon in conventional manner and/or by admixture with overbased alkaline earth metal sulphonates of the type hereinbefore described. Such overbased salts may also contain an alkyl substituted phenol or metal phenate, optionally containing more than one alkyl substituent on the aromatic nucleus.

Alternatively the basic additives may consist of alkaline earth metal or magnesium alkyl phenates, preferably having alkyl chains containing at least 9 carbon atoms, the corresponding sulphurized phenates or metal phenate sulphides or metal alkyl salicylates.

The basic additive concentrates may be employed in the lubricating compositions of the present invention in amounts of 0.5 to 7.5%, preferably 1.0 to 5.0%, by weight based on the total weight of the compositions.

In another aspect the present invention also provides an additive package comprising a mineral oil having dissolved or dispersed therein from 5 to 50 preferably 10 to 35%, by weight based on the total weight of the additive package, of:

(a) a nitrogen-free random copolymer of one or more alkyl methacrylates and one or more alkyl acrylates, preferably prepared by copolymerizing one or more alkyl methacrylate comonomers with one or more alkyl acrylate comonomers, the copolymer being composed of up to 65% alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units present in the copolymer and from 5 to 90%, preferably =10 to 60%, by weight based on the total weight of the additive package of:

(b) an alkaline earth metal containing detergent having a total base number greater than 40.

It will be understood that the preferred features hereinbefore described for additives (a) and (b) of the lubricating compositions of the present invention are also applicable to additives (a) and (b) of the additive packages of the invention.

It will also be understood that the lubricating compositions and additive packages of the present invention may optionally contain additional conventional additives such as antioxidants; dispersants, especially the ashless dispersants of the succinimide type; corrosion inhibitors; pour point depressants and other conventional additives as desired.

The invention will now be illustrated with reference to the following examples:

EXAMPLES 1 TO 3 Alk'yl methacrylate/acrylate copolymers were prepared by the following technique:

Comonomers (150 g.) and a commercially available mineral oil polymerization solvent of viscosity 31 cst. to 33 cst. at 100 F. (195 g.) were mixed and purged with nitrogen for 1.5 hours at 85 C. in an oil bath fitted with a thermostat.

A solution of t-dodecyl mercaptan in the solvent oil was prepared having a concentration of 7.5 g. t-dodecyl mercaptan per 100 grams of solution. 8 g. of the mercaptan solution and 1.2 g. of lauroyl peroxide were then added to the polymerization mixture and the internal temperature of the polymerization mixture was allowed to rise to 90 C. where it was maintained constant. Further additions of the peroxide initiator and mercaptan solution were made as follows:

Time after Mercapcommencement of tan polymerization solu- Perox- (mins) tion (g.) ide (g.)

The polymerization was stopped 2 hours after commencement by the addition of 5 drops 2,4dimethyl-6-t-butyl phenol.

The products prepared by this technique were as follows:

Example 1 A solution in mineral oil of a copolymer (40% by weight concentrate) containing 20% 2-ethylhexyl acrylate units and mixed alkyl methacrylate units, the methacrylate units being derived from a mixture of 50% butyl methacrylate units and 50% mixed cetyl and stearyl methacrylate units.

Example 2 A solution in mineral oil of a copolymer (40% by weight concentrate) the same as in Example 1, except that it contained 20% butyl acrylate units in place of the 20% 2-ethylhex'yl acrylate units.

Example 3 (i) Conventional V.I. improvers Polymer Concentrate A, a mineral oil concentrate (40% by weight) of a polymethacrylate copolymer containing 60% butyl methacrylate units and 40% mixed cetyl and stear'yl methacrylate units.

Polymer Concentrate B, a commercially available alkyl acrylate polymer concentrate (approximately 26% solids).

Polymer Concentrate C, a concentrate (approximately 38% solids) of an alkyl methacrylate copolymer containing about 40% butyl methacrylate units and about 60% mixed C1248 methacrylate units.

Polymer Concentrate D, a concentrate (approximately 44% solids) of a copolymer of about 17% by weight methyl methacrylate and about 83% by weight mixed C1248 alkyl methacrylates.

Polymer Concentrate E, a commercially available concentrate (approximately 40% solids) of a copolymer of mixed alkyl methacrylates.

Polymer Concentrate F, a concentrate (approximately 40% solids) of a copolymer of about 22% methyl methacrylate units and 78% C alkyl methacrylate units.

(ii) Acrylate/methacrylate V.I. improvers Polymer Concentrate G, the product of Example 1.

Polymer Concentrate H, the product of Example 2.

Polymer Concentrate J, the product of Example 3.

Polymer Concentrate K, a concentrate (approximately 40% solids) of a copolymer containing 20% butyl acrylate units, 40% butyl methacrylate units and 40% mixed cetyl and stearyl methacrylate units.

Polymer Concentrate L, a concentrate (approximately 40% solids) of a copolymer containing 50% butyl acrylate units, butyl methacrylate units and 40% mixed cetyl and stearyl methacrylate units.

Polymer Concentrate M, a concentrate (approximately 40% solids) of a copolymer containing 50% 2-ethylhexyl acrylate units, 18.5% methyl methacrylate units and 31.5% mixed C alkyl methacrylate units.

Polymer Concentrate P, a concentrate (approximately 40% solids) of a copolymer containing 20% 2-ethylhexyl acrylate units, 30% methyl methacrylate units and 50% mixed C alkyl methacrylate units.

Polymer Conncentrate P, a concentrate (approximately 40% solids) of a copolymer containing 50% ethyl acrylate units, 4% methyl methacrylate units and 46% C alkyl methacrylate units, C alkyl methacrylate units consisting of 63% C and 37% C1248 alkyl methacrylate units.

Table I shows viscosity data for 10% solutions in mineral oil of certain concentrates. The mineral oil was a 150 Solvent Neutral oil having a viscosity index (without copolymer) of about 101 to 105 and the polymethacrylate copolymer (Polymer A) was prepared by the same technique as the copolymers of Examples 1 to 3.

In order to evaluate the thermal stability of the copolymers of Examples 1 and 3, in combination with a basic additive, as compared with similar blends containing polymers not of the invention, mineral oil blends of concentrates of the polymers were subjected to Panel Coker Tests. In these tests a sample of the mineral oil blend was contained in a sump which was fed by a chicken feed to maintain a constant level of oil. The oil was splashed continuously, for 24 hours, onto a sloping aluminium panel maintained at a pre-selected temperature, by means of wires on a rotating spindle.

The weight change and appearance of the panels were observed after test, the appearance of the panels being assigned merit ratings which were determined by comparison with a set of panels divided into groups of seven. Where the panels were merely stained these panels were given numbers 1 to 7 in increasing order of staining, i.e. number 1 was practically clean and number 7 was black, the sufiix 0 indicating ordinary staining. In the second group the same numbers were assigned but the suflix L was used to indicate that the panel was lacquered. Similarly, in group 3 the sufiix S showed the panel was sooted. The mineral oil blend used in these tests con sisted of a 150 Solvent Neutral mineral oil having kinematic viscosities of about 33.2 cst. and 5.2 cst. at 100 F. and 210 F. respectively, in which was dissolved 0.9% by weight of a zinc mixed isopropyl/capryl dithiophosphate, 3.0% of a commercially available ashless dispersant consisting of a 40% concentrate in mineral oil of a polyisobutenyl, succinimide containing about 2% N and 2.8% of an overbased calcium petroleum sulphonate having a TBN of about 300, together with a small amount of the polymer to be tested (in the form of a mineral oil concentrate). The amount of the polymer employed in each case was selected such that the tested blends all had approximately the same initial viscosity.

The results obtained in the Panel Coker Tests are set out in Table 2.

Engine tests were also carried out to illustrate the properties of lubricating compositions containing mixtures of the acrylate/methacrylate copolymers and basic additives. These tests were carried out in Petter AV-1 engines in accordance with the conditions set out in Ministry of Defence specification DEF-2101-D. The mineral oil blends tested in this manner consisted of 2.8% by Weight of Hitec E627 (Hitec E627 is a commercially available basic detergent based on an overbased barium salt of a phosphosulphurized polyisobutylene and having a TBN of from 70 to 85), and 0.9% by weight of the same zinc dialkyl dithiophosphate as was employed in the Panel Coker Tests dissolved in mineral oil, together with sufficient polymer concentrate to provide an initial viscosity of about 17.2 cst. The mineral oil was a 500 Solvent Neutral mineral oil having viscosities of about 11.0 and 11.2 cst. at 100 F. and 210 F. respectively.

The results of the Petter AV-l tests are set out in Table 3. In this test various parts of the piston are examined after the test and are assigned merit ratings of from 0 to 10 according to cleanliness, the composite merit rating A-+B+C (see Table 3) usually being considered the most important criterion. However, since the top groove rating was affected more by fuel combustion than by the lubrieating oil employed and all the polymers tested gave top groove ratings which fell within tolerable limits, a rating (D) was obtained for the average 2nd, 3rd and 4th groove ratings only. Moreover the piston skirt ratings (A) were all very similar. It was considered therefore that the composite rating D +B+E (E being the piston undercrown rating) was a better comparison of the properties of the tested lubricant compositions than A+B+C.

Further Petter AV-1 engine tests were carried out under the same conditions, but employing SAE 10W/30 lubricants formulated to meet the Ford ESEM2C-101-B specification and containing 2.8% of overbased calcium benzene sulphonate (TBN 300). The performance of a blend containing Polymer Concentrate D was compared with an otherwise identical blend containing Polymer Concentrate N and the results are shown in Table 4.

Further engine tests were also carried out in accordance with a High Temperature Petter W1 procedure. In these tests the engine employed was a Petter W1 laboratory engine built to Standard IP schedule except for lead/ bronze big end bearing shells having a lead/indium overlay in place of the normal copper/lead shells, since it was considered that the latter had insufiicient oxidative corrosion resistance to withstand the severity of the test procedure. After completion of the running in of the engine according to the standard schedule, the tests were carried out under the following conditions.

Oil fill 900 gms.

Speed 1500 rev./rnin.

Load 3 BHP.

Jacket temperature 350: *:3 F.

Slump temperature 325 13 F.

Hot spot temperature 383-410 F.

Fuel flow 113:0.5 sec. per 50 ml.

Oil pressure 10-11 p.s.i.

Duration 48 hours (subject to oil consumption) Coolant 100% ethylene glycol.

Fuel DEF 2405 C octane reference gasoline.

The two mineral oil blends tested according to this procedure were fully formulated blends, both containing equal amounts of an antioxidant/dispersant/low base number (approximate TBN=16) calcium petroleum sulphonate detergent additive package, and each containing 1.5% of an overbased calcium sulphonate detergent concentrate containing 11.3% Ca and having a TBN of 275 to 300. In addition both blends contained a mineral oil concentrate of the polymer to be tested. The base mineral oil for the fully formulated blends was a mixture of a 150 Solvent Neutral mineral oil having viscosities of about 34 cst. and 5.4 cst. at F. and 210 F. respectively and a 500 Solvent Neutral mineral oil having viscosities of about 112 cst. and 11.5 cst. at 100 F. and 210 F. respectively, and was blended with the additives. In addition the blend containing Polymer C concentrate also contained 0.1% by weight of a pour point depressant. The object of this test was to assess the tendency of an oil to thicken in service under high temperature conditions.

The results of the W1 engine tests are shown in Table 5.

From the results set out in Table 1 it will be noted that the acrylate/methacrylate copolymers used in the present invention gave similar viscosity lifts and not greatly inferior viscosity index improvement to the conventional polymethacrylate V.I. improver, Polymer A.

The Panel Coker Tests in Table 2, particularly the tests at 325 C. and 350 C., demonstrated the greater thermal stability of blends containing both an acrylate/ methacrylate copolymer and a basic calcium sulphonate, as compared with similar blends in which the copolymer was replaced by a conventional polymethacrylate.

The Petter AV1 engine tests in Table 3 showed that whereas four blends containing different polymethacrylates in conjunction with a basic detergent gave inferior piston ratings (D+B+E) to the oil containing only the detergent, the two blends containing methacrylate/acrylate copolymers actually gave improved ratings. Similarly, it is shown in Table 4 that the blend containing Polymer Concentrate N gave a superior rating to that of the blend containing Polymer Concentrate D.

The Petter W-l engine tests in Table 5 clearly demonstrated the superiority of the blend containing the concentrate of Example 1 over that containing Polymer C concentrate, the viscosity increase of the oil being very substantially reduced and the insolubles content halved. Furthermore the test on Polymer C had to be terminated at 46 hours because of the large amount of oil that had been volatilized.

In order to demonstrate the gelling tendencies of the additive combinations of the present invention in comparison with similar combinations in which component (a) was a polymethacrylate or a polyacrylate, a series of tests were carried out in which the polymer concentrates were mixed with equal weights of various overbased detergents (b) at room temperature and the consistency examined after standing for 24 hours. The results are given in Table 6, from which it will be seen that mixtures containing a wholly acrylate polymer (Polymer Concentrate B) gave, in three instances out of five, very severe thickening, which did not occur in the other cases. Similar tests were carried out using unequal Weights of components (a) and (b), and the results are shown in Table 7.

In order to evaluate the dispersancy characteristics of the additive combinations of the invention, spot tests were carried out. Additives were blended with used SAE 30 engine oil which had contained antioxidant as the only additive. The samples so obtained were stored for 6 hours the test sample had been absorbed into the paper. The specific dispersancy of each test additive was calculated using the equation:

Specify Dispersancy 5 X 100 wherein d=diameter of the central spot and D=diameter of the sludge front.

The results of these tests are shown in Table 8 and demonstrate that the additive combination employed in the lubricating compositions of the present invention are as effective dispersants in this test as a commercially available dispersant V.I. improver despite the individual components of the combination showing relatively little dispersancy characteristics.

In order to further evaluate the dispersancy characteristics of the additive combinations employed in the present invention, paper strip chromatographic tests were carried out by the following procedure. Test samples were prepared by blending additives with an SAE 30 engine lubricant base oil. The samples were then mixed with an equal volume of the same base oil in which had been dispersed, by shaking for 24 hours, 4% of Spheron 9-27 m, particle size carbon black. 2 gms. of each of the resulting mixtures were heated at 100 C. for 5 hours in 20 gm. vials of 20 mm. diameter. Thereafter, a strip of Whatman filter paper Qualitative No. 1 was suspended with its base immersed to a depth of 1-2 mm. in the oil sample and chromatography was allowed to take place at 100 C. for 16 hours. The R, value of each additive combination was calculated as the ratio of the distance travelled by the carbon black front to the distance travelled by the oil front. The results are shown in Table 9 and demonstrate that the additive combinations employed in the present invention are as etfective dispersants in this test as a conventional succinimide dispersant additive, despite the individual components of the combination showing relatively little dispersancy characteristics.

TABLE 1.VISCOSITY AND V.I. DATA at 100 C., after which one drop of each sample was al- 53322 Viscosity (0st) lowed to fall onto a sheet of chromatographic paper. This content of Viscosity produced a spot. After being allowed to develop over a Polymer Concentrate polymer 2100 index eriod of one week the s ot usuall became urr 11 ed olymer A 40- 0 55- 3 9. 2 160 g ht l d t S d f Polymer G 4o. 0 58.36 9. so 152 Y {2 F 00 Ore 011 6r flng, 011 fir P P y 0 Polymer G (repeat).... 40. 0 58.82 9. 41 153 WhlCh indicated the sludge front attributable to the migraj l i 5 8-8 gg-gg 3-32 2 tion of dispersed sludge away from the central spot where o yme 14 TABLE 2.PANEL COKER TESTS None 1 Polymer concentrate A(11. 8%) G (11. 8%) J (12. 7%) B (5. 8%) C (6. 0%)

Panel temperature, 300 0.:

Weight gain (mg.) 70. 9 45. 0 81.0 53. 8 57 54 Rating 5/6 5/6 5/6 5/6 5/6 6/6 3 O 9 O I O I O l O I 0 Panel temperature, 325 0.:

Weight gain (mg) 697 72. 0 153 267 129 50 Ratin 7 6 6 7 6 5/6 L/S 0/5 I O/S L/S 4 S 1 0 Panel temperature, 350 0.:

Weight gain (mg.) 748 119 119 677 1, 446 54 Rating 7 6 7 7 6 L OIL OIL L 5 S Q 0 t Base blend only. 1 Soot at edges. 8 Small areas of lacquer. 4 Lacquer at bottom. l Thin patchy laquer. Thin soo TABLE 3.-PETTER AV-l ENGINE TESTS Polymer concentrate in test blend G (9. 0%) H(9. 4%) A(9. 4%) 0(4. 6%) O (4. 6%) D (4. 6%) E (4. 0%) None 1 Piston skirt rating (A) 9. 9 10. 0 9. 9 10. 0 9. 9 10. 0 9. 9 10. 0 Average lands rating (B). 8. 9 8. 5 7. 8 5. 7 5. 1 7. 1 7. 3 7. 8 Average grooves rating 8. 5 8. 7 7. 2 5. 9 5. 2 7. 1 5. 2 6. 8 Average rating 2nd, 3rd and 4th grooves only (D) 8. 4 9. 0 7. 5 6. 0 5. 3 6. 4 6. 5 7. 5 Piston Undercrown rating (E) 6. 0 5. 3 4. 8 6. 0 5. 0 4. 0 5. 9 5. 8 A+B+C 27. 3 27. 2 24. 9 21. 6 20. 2 24. 1 22. 4 24. 6 D+B-|-E. 23. 2 22. 8 20. 2 17. 7 l5. 4 17. 5 18. 7 21. 1 Total ring Weight loss (mg.) 113 155 112 81 196 133 122 Oil consumption (lo/hr.) 0. 008 0. 007 0. 038 0. 020 0. 012 0. 013 0. 0266 0. 003 Remarks: DEF2101-D Pass Pass Fail Fail Fail Fail Fail Fail 1 Repeat. 1 Base blend only.

' Top ring 6% cold stuck very high oil consumption.

TABLE 4.-PETTER AV-l ENGINE TESTS TABLE 5Continued Polymer concentrate in test blend N (5.05%) D (4.68%) Polymer concentrate in blend G (10.6%) C (6.5%)

Piston skirt rating (A) 9. 9 9. 9 Piston undercrown rating 6. 9 6. 3 Average lands rating (B) 7. 4 6. 1 Oil consumption (g.) 412 532 Average grooves rating (C) 7. 3 5. 5 5 Oil analysis: Average rating 2nd, 3rd and 4th grooves only (D) 7. 2 6. 6 Kinematic viscosity at 100 F. (KVIOO): Piston Undercrown rating E 8. 5 6.8 Initial, cs 132.38 120. 8 A+B+C 24. 6 21.5 Final cs 713.0 2, 041. D+B +E 23.1 19. Increase, percent 430 1, 600 Total ring weight loss (mg.) 128 178 210: Oil consumption (lb./hr.)-.. 0.015 0. 029 Initial, cs 15. 95 16. 7 Remarks: DEF-2101-D Pass Fai Final, cs 47 96 75.0 Increase, percent. 200 350 Total Acid Number (TAN initial 3. 4 2. 6 TABLE 5.-PETTER W1 ENGINE TESTS Final m8 Polymer concentrate in blend G (10. 6%) C (6. 5%) i fi i Number (TBN): 5' 9 7 Final 5. 4 1. 7 fag gg %g t"" 2:2 Insolubles content of blend at end of test, Piston grooves rating (0) 4. 1 4. 7 percent 45 95 A+B+C 17. 1 18. 1

TABLE 6.GELLING TESTS COMPONENT (a) Component (b) Polymer concentrate A Polymer concentrate G Polymer concentrate J Polymer concentrate B 26rgrerbased sulphurized phenate No viscosity increase-.-- No viscosity increase No viscosity increase Small viscosity increase.

Callc iliamNi gozerbased alkyl benzene sulphonate do do do Very viscous rubbery. Hitec E627 do do do Small viscosity increase.

TABLE 7.GELLING TESTS Component (b) Component (a) Parts by Polymer concentrate F Polymer concentrate K Polymer concentrate L Polymer concentrate B Component Weight (7.0 parts by wt.) (8.0 parts by wt.) (8.0 parts by wt.) (7.0 parts by wt.) Calcium overbased alkyl benzene 2. 0 Small viscosity increase. Small viscosity increase. No viscosity increase Very viscousrubbery."

sulphonate (TBN 300). Magnesium overbased alkyl ben- 1. 5 No viscosity incr e do do Large viscosity increase.

zene sulphonate (TBN 400). Hitec 680 1 (TBN 76) 2. 0 Small viscosity increase- No viscosity increase --do Very vlscousrubbery".

l Commercially available basic detergent based on an overbased barium salt of a phosphosulphurized polyisobutylene.

TABLE 8.--SPECIFIC DISPERSANCY TESTS Component (a) Component (b) Percent Percent Component dosage Component dosage dispersancy Polymer concentrate F- 8. 0 i 0 Polymer concentrate M. I 8. 0 0 Calcium overbased alkyl benzene sulphonate (TBN 300). 3. 0 4 Polymer concentrate F- 8. 0 .....do. 3. 0 24 Polymer concentrate M- 8. 0 0-. 3. 0 48 Commercially available d1 pet of alkyl 8.0 48

methacrylate/N-vinyl-2-pyrrolidone copolymer.

TABLE 9.--PAPER STRIP CHROMATOGRAPHY TESTS Component (8.) Component (b) Percent Percent Component dosage Component dosage R: value Polymer concentrate M 8. 0 0. 01 Polymer concentrate P 8. 0 0. 01 Polymer concentrate F 7. 0 0. 02 Calcium overbased alkyl benzene sulphonate (TBN 2. 0 0. 09

300) containing soap. Polymer concentrate M... 8. 0 do 2.0 0. 54 Polymer concentrate P. 8. 0 do 2. 0 0. 53 Polymer concentrate F. 7. 0 2. 0 0. 10 Polymer concentrate F 7. 0 Calcium overbased alkyl benzene sulphonate (TBN 2. 0 0. 05

300) containing 20% soap. Polymer concentrate M 8. 0 2. 0 0. 47 Polymer concentrate P 8. 0 Calcium overbased alkyl benzene sulphonate (TBN 2. 0 0.

300) containing 20% soap. Polymer concentrate F 7. 0 2. 0 0. 19 Mzggesium overbased alkyl benzene sulphonate (TBN 2. 0 0. 09 Polymer concentrate M. 8 0 do 2. 0 0. 27 Polymer concentrate P 8.0 do 2. 0 0. 27 Polymer concentrate F 7.0 do 2.0 0.08 Hitec E638 (commercially available ashless succinimide- 3.0 0.86

type dispersant containing about 2.0% nitrogen).

We claim: H

1. A lubricating composition comprising (i) from 85 to 99% by weight based on the total weight of the composition of a mineral oil of lubricating viscosity and (ii) from 1 to 15% by weight based on the total weight of the composition of a combination of additives consisting essentially of (a) viscosity index improving amounts of a nitrogen-free random copolymer of one or more alkyl methacrylates and one or more alkyl acrylates, the copolymer being composed of from about 5% to 65% alkyl acrylate units based on the total number of alkyl acrylate and alkyl methacrylate units present in the copolymer and (b) a detergent amount of an overbased alkaline earth metal detergent having a total base number greater than 40.

2. A composition according to claim 1 wherein the random copolymer comprises from 15 to 25% alkyl acrylate units based on the total number of alkyl methacrylate and alkyl acrylate units.

3. A composition according to claim 2 wherein the alkyl acrylate units contain from 6 to 12 carbon atoms.

4. A composition according to claim 1 wherein the alkyl acrylate units are selected from the group consisting of butyl acrylate, 2-ethylhexyl acrylate and mixtures of butyl acrylate and 2-ethylhexyl acrylate units.

5. A composition according to claim 1 wherein the alkyl methacrylate is a mixture of 60 mole percent butyl methacrylate and 40 mole percent mixed cetyl and stearyl methacrylate.

6. A composition according to claim 1 wherein the random copolymer is present in the lubricating composition in an amount of from 1 to 5% by weight based on the total weight of the composition.

7. A lubricating composition comprising (i) from 90 to 98% by weight based on the total weight of the composition of a mineral oil of lubricating viscosity and (ii) from 2 to by weight based on the total weight of the composition of a combination of additives consisting essentially of (a) from 1 to 5% by weight based on the total 12 weight of the composition of a nitrogen-free random copolymer prepared by copolymerizing one or more alkyl methacrylate comonomers with one or more alkyl acrylate comonomers each alkyl acrylate unit containing from 6 to 12 carbon atoms, the copolymer being composed of from 15 to 25 alkyl acrylate units based on the total number of alkyl acrylate and alkyl methacrylate units present in the copolymer 1 and (b) a detergent amount of an overbased alkaline earth metal containing detergent having a total base number greater than 40.

8. An additive package comprising a mineral oil having dissolved or dispersed therein.

(a) from 5 to by weight based on the total weight of the additive package of a nitrogen-free random copolymer of one or more alkyl methacrylates and one or more alkyl acrylates, the copolymer being composed of about 5% to alkyl acrylate units based on the total number of alkyl acrylate and alkyl methacrylate units present in the copolymer, and (b) from 5 to by weight based on the total weight of the additive package of an overbased alkaline earth metal detergent having a total base number greater than 40.

References Cited UNITED STATES PATENTS 2,991,246 7/ 1961 Kleinholz 25233.4 X 3,350,308 10/1967 McMillen 25233.4 X 3,368,971 2/1968 Retzloff et al. 25233.4 3,451,931 6/1969 Kahn et al. 25251.5 A X 3,340,193 9/1967 Fields et al 25256 R 3,264,376 8/1966 Bauer 25256 R 3,166,508 1/1965 Fields 25256 R 2,604,453 7/1952 Popkin 25256 R 2,091,627 8/1937 Bruson 25256 R WARREN H. CANNON, Primary Examiner US. Cl. X.R. 25256 R 

